Examples of the devices available for achieving fluidic control are the fluidic diode, the vortex amplifier and the jet pump. Devices such as these, in which no moving parts are employed, may be combined to achieve control functions which customarily are achieved only by the use of mechanically movable valve members. Thus, it is possible to achieve with combinations of fluidic devices the functions of pressure relief and pressure regulation. An object of the present invention is to provide a form of fluidic flow control which will achieve a shut-off function.
According to the present invention, a method of arresting a mainstream flow of fluid comprises placing the mainstream in permanently open communication with a control stream, reciprocating the control stream back and forth across a lateral outlet to inhibit access by the mainstream to the outlet, and discontinuing reciprocation of the control stream when it is required that the arresting function should cease for resumption of full flow of the mainstream to and through the outlet.
A control flow of a reciprocating nature is advantageous in that it can be provided by the interconnection of alternately pressurised reservoirs of the control flow fluid. If instead of being pressurised alternately, these reservoirs become subject to balanced pressures less than that of the mainstream in the region of intercommunication with the control stream, the reciprocation of the control stream is discontinued and a control state established whereby full flow of the mainstream can occur.
In terms of apparatus, the invention provides a fluidic valve device for arresting a mainstream flow of fluid which device comprises a control stream passage, a mainstream inlet and a mainstream outlet both in permanently open communication with the passage but with one of them branched so as to open into that passage at locations disposed symmetrically to either side of a lateral opening of the other into the same passage, means to reciprocate a control stream of fluid in the passage back and forth across the lateral opening for inhibiting access of the mainstream from the inlet to the outlet, and means to discontinue selectively the reciprocation of the control stream so that full flow of the mainstream to and through the outlet may occur.
More particularly the fluidic valve device comprises a control passage including nozzles opposing each other in axial alignment across an interspace, a mainstream outlet opening into the interspace through a diffuser, and communications connecting a mainstream inlet with the control passage at locations disposed symmetrically to either side of the interspace which communications are permanently open but include means effective to restrict flow in the direction towards the inlet, there being also a means as already mentioned to reciprocate a control stream of fluid in the passage, and hence alternately from one nozzle to the other across the interspace, so that the mainstream is isolated substantially not only from the outlet but also from the control passage by virtue of control stream back pressure built up at the flow restricting means.